Analyzing Cosmic Ray Spectral Features

Recent cosmic ray direct measurements have revealed a hardening and softening feature for multiple elemental spectra, creating a bump structure. A progressive hardening at ~200 GV has been reported by CREAM, ATIC-2, PAMELA, AMS-02, CALET, and DAMPE. A softening in the proton spectrum has been reported at ~10 TeV by CREAM, NUCLEON, ISS-CREAM, CALET, and DAMPE, with a softening in the helium spectrum seen in a few tens TeV by NUCLEON, DAMPE, and CALET. A similar softening is indicated in the carbon and oxygen spectra as well. We investigated the cause of these spectral features using the numerical cosmic-ray propagation code GALPROP. To study the hardening, three cases were considered using: (1) a diffusion break, (2) source injection breaks, and (3) a combination of both. Focus was given to the softening using additional source injection breaks. Results will be compared to compiled cosmic ray elemental spectra and ratio data. The implications of these features will also be discussed.